1. Field of the Invention
The invention relates generally to the field of digital tape recording. More particularly, the invention relates to head lifting apparatus for digital tape systems.
2. Discussion of the Related Art
Headlift mechanisms are known to those skilled in the art. For example, a conventional headlift mechanism typically includes a headlift bracket coupled with a stepper motor (the combination herein referred to as the xe2x80x9cheadlift assemblyxe2x80x9d). The read/write transducer head of a data storage system is mounted on the bracket. The bracket is coupled with other portions of the tape drive via a head guide assembly (HGA) frame. The HGA includes the headlift assembly and the HGA frame. The stepper motor typically includes a threaded shaft that rotates to cause the head and the headlift bracket to move upwards or downwards across a digital tape. This movement positions the head over the tape""s data tracks. Each data track runs along the length of the tape. Multiple data tracks are disposed vertically, one above the other, over the width of the tape. One of the key capacity limitations of tape storage systems has been that only a limited number of data tracks could be placed over the width of the tape because of the headlift assembly could not accurately place the head over the tracks.
FIG. 1 shows a portion of a tape drive including a conventional HGA 100. The conventional HGA includes conventional stepper motor 110, HGA frame 120, and headlift bracket 130. HGA guide pin 140 is mounted on HGA frame 120 to provide head alignment accuracy across the width of the tape.
Conventional stepper motor 110 includes a rotating shaft, which is typically a lead-screw 112 and a circular top surface 114. Lead-screw 112 extends upwards from circular top surface 114.
Headlift bracket 130 includes a platform 132 for mating with the head, and a conventional arm (not shown in FIG. 1) extending horizontally from the platform. The conventional arm typically has an opening and a nut configured to receive lead-screw 112, which when fastened to the lead-screw cause the HGA to move upwards or downwards in response to movement of the lead-screw. Neither the nut nor the opening is shown in FIG. 1. Conventional stepper motor 110 controls movement of lead-screw 112. Any rotation about the threads of lead-screw 112 results in movement of the headlift assembly upward or downward along the screw.
HGA guide pin 140 is mated to headlift bracket 130 using a claw 150 disposed on the bracket. Claw 150 is attached to HGA frame 120. Claw 150 engages HGA guide pin 140 and attaches HGA guide pin 140 to HGA frame 120.
Headlift bracket 130 is adjusted so that the lifting surface 160 (the mounting surface for the transducing head) is parallel to HGA frame 120""s mounting surface plane. As shown in FIG. 1A, the mounting surface plane is defined at points 165. These three mounting surfaces of the HGA are known collectively as xe2x80x9cDatum A.xe2x80x9d The adjustment of the lifting surface 160 relative to the mounting surface is called xe2x80x9cadjusting azimuth and zenith.xe2x80x9d
Returning to FIG. 1, once the azimuth and zenith adjustment is complete, claw 150 will generally not be parallel with HGA guide pin 140. To overcome a potential binding of claw 150 with HGA guide pin 140 a loosely fitting claw bushing 152 is installed between the claw and the pin. In some conventional HGA designs, claw 150 includes a claw pin 154 extending upwards from the rest of the claw. Claw bushing 152 can snap onto claw pin 154. Claw bushing 152 is allowed to pivot about claw pin 154 (i.e., rotate about claw 150) to relieve the binding of the claw and HGA guide pin 140.
As headlift bracket 130 moves up and down along its designated length of travel, the relationship between claw 150 and HGA guide pin 140 changes. The relationship changes because of the loose fit between HGA guide pin 140 and claw 150 at the height of claw bushing 152 that potentially results in a non-parallel condition between claw 150 and HGA guide pin 140. When claw 150 is not parallel with HGA guide pin 140, a first side of claw 150 can rub HGA guide pin 140 at the bottom of the headlift travel; while the opposite side of the claw can rub HGA guide pin 140 at the top end of the headlift travel. The change in contact from one side of claw 150 to the other side can cause headlift bracket 130 to rotate while lifting. Such rotation causes an undesired linear movement of the head.
Conventional headlift mechanisms typically have large lift error tolerances that can range up to approximately 450 micro-inches. However, because newer tape drives have more and narrower data tracks, as well as higher tape speeds to meet demands for increased storage, tighter headlift tolerances have been imposed. As a result, the first pass yields and final yields for building conventional HGA have become unacceptably low.
The low manufacturing yields for headlift assemblies applying the prior art approach to high speed and high storage density tape drive systems result in much higher cost. The low manufacturing yields are caused by tolerance problems arising from the non-parallel condition of claw 150 and HGA guide pin 140. If the alignment errors for the HGA components are too large, then HGA guide pin 140 and claw 150 are subject to a binding condition during movement of the HGA components during azimuth and zenith alignment. Therefore, what is also needed is a solution that meets the above-discussed headlift accuracy requirements in a more cost-effective manner. An HGA assembly that can position the head more precisely as required by new high data capacity, high-speed tape drive systems, and still be manufactured with acceptable yields is needed
A headlift system according to the present invention includes a guide pin that is integrated with a stepper motor having a shaft, and a bracket coupled to a magnetic tape transducer head. The bracket is configured to couple with the guide pin and the stepper motor shaft to provide more accurate movement of the head than conventional headlift systems.
The stepping motor controls the rotational movement of the shaft. The shaft extends from the stepping motor along a first axis and rotates about this axis. The guide pin extends from the stepping motor in approximately the same direction as the first axis. The guide pin is spaced apart from the shaft.
The head lift system also includes a bracket. The bracket includes a head mating surface, an arm, and a bushing. The arm extends horizontally from the head-mating surface. The arm includes a first opening aligned to receive the shaft, and a second opening aligned to receive the guide pin. The bushing is disposed in the second opening. The bushing is coupled with the guide pin to limit movement of the head radially, and to limit movement of the head circumferentially relative to the shaft.
The head lift system also includes a shaft-linking element. The shaft-linking element is positioned and dimensioned for coupling with the shaft.
These and other aspects of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings.